Affiliation:
1. Whitney Laboratory, University of Florida, Gainesville, Florida 32601
2. Deparments of Zoology and Neuroscience, Center for Smell and Taste, and McKnight Brain Institute, University of Florida, Gainesville, Florida 32601
Abstract
We report that a Na+-activated nonselective cation channel described previously in lobster olfactory neurons, in which phosphoinositide signaling mediates olfactory transduction, can also be activated by Ca2+. Ca2+activates the channel in the presence of Na+, increasing the open probability of the channel with a K1/2of 490 nM and a Hill coefficient of 1.3. Ca2+also increases the sensitivity of the channel to Na+. In some cells, the same channel is Ca2+insensitive in a cell-specific manner. The nonspecific activator of protein phosphatases, protamine, applied to the intracellular face of patches containing the channel irreversibly eliminates the sensitivity to Ca2+. This effect can be blocked by okadaic acid, a nonspecific blocker of protein phosphatases, and restored by the catalytic subunit of protein kinase A in the presence of MgATP. The Ca2+-sensitive form of the channel is predominantly expressed in the transduction zone of the cells in situ. These findings imply that the Ca2+sensitivity of the channel, and possibly its regulation by phosphorylation, play a role in olfactory transduction and help tie activation of the channel to the canonical phosphoinositide turnover pathway.
Publisher
American Physiological Society
Subject
Physiology,General Neuroscience
Cited by
6 articles.
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